[Source: NOAA Earth System Research Laboratory, Physical Sciences Division, http://www.esrl.noaa.gov/psd/ ]
The timeseries of SST anomalies averaged over 60W to 20W, 6N to 18N and 20W to 10W, 6N to 10N. Data is obtained from the COADS
dataset for 1951-2000. Anomalies were calculated relative to the 1951-2000 climatology, smoothed by three months running mean
procedure and projected onto 20 leading EOFs. Month of data is the center of the 3 months that are smoothed.
See: http://www.esrl.noaa.gov/psd/data/climateindices/list/#NTA